Telephone system



April 7, 1942. w. PINELL TELEPHONE sYsTEM Filed Jan. '8,' 1940 5 sheets-sheet 1 Attorney W. PINELL TELEPHONE SYSTEM April 7, 1942.

Filed Jan. 8, 1940 3 Shee'iZs-Sheetl 2 April 7, 1942. w. PINELL.

TELEPHONE sYsTEM Filed Jan. 8, 1940 3 Sheets-Sheet 5 Patented Apr. 7, 1942 insist erre nur mit beschrnkter Haftung, Bertin, Germany, a corporation of Germany Application January 8, 1940, Serial No. 312,811

i rice iin Germany .ianuary 17, 1939 (Ci. itil- 27) 14 Claims.

The present invention relates to automatic .telephone systems in which the connections incoming from outside exchanges are set up over numerical impulsing devices used in outgoing connections from this exchange station. Thus for setting up an outgoing connection, after selection of the required subscribers line over a setting path and connectionof a numericalimpulsing device, also used for outgoing connections, to the selected line, this numerical impulsing device is set by the dialled impulses, which are controlled by that station setting up the incoming connection, e. g. by an operator, andare sent over the setting path. The numerical impulsing device then has access to the calling line over means usedl only for incoming connection directions.

With this system therefore, for setting up the connecting path it is necessary to have the impulse series characterising the calling exchange as well as the impulses corresponding to the nurnber-of the required subscriber. If this exchange receives calls from several outside exchanges to pass to line then, especially in heavy traffic, mistakes in characterising the calling exchange are easily possible, for the calling subscriber sends only the number of the required subscriber.

If the impulses for setting up the incoming connection are sent out, for example from an impulse transmitter by a key set, it is necessary to provide additional switch means in order that the necessary impulse trains should be sent out for gaining access to the required subscribers line. Switch means must be provided which make possible the transmission of the additional numerical impulse train or trains, the number of which are adjusted to correspond with the selecting stage over which the line is reached. As a rule the line is connected to th'e first group selector or in smaller systems to a certain bank of the iinal selector. In order not to decrease the capacity of the system too greatly it may also be necessary to connect the lines to the second or third group selectors, or, if a smaller system is in question to individual line contacts of the iinal selector. Therefore two or three additional numerical impulse series are necessary.

The additional impulse for setting the impulsing device, also used for outgoing traiiic, cannot be sent out directly after dialling if the required subscribers line is engaged. transmitter must therefore be furnished with further switch means which give rise to the transmission of the additional impulses only if after notiiication of the required subscriber, who however is engaged in the existing connection is dis- The numerical "l connected and a free impulse receiver is readyv to receive the dialled impulses for setting up the talking connection.

The present invention removes all these diiculties in that after selecting the line of a subscriber required for an incoming connection over a setting path and connecting a numerical impulsing device also used for outgoing connections to this line, under the control of a marking signal for the incoming direction, the switch means functioning to set up the connection are operated and automatically set the numerical impulsing device on the calling line. n

In using the arrangement laccording to the invention the station setting up of the incoming connection need only effect the transmission of impulses corresponding to the required subscriber. The impulse senders are provided with no switch means for other purposes (additional impulses and transmission of the same dependent on special conditions). False connections are moreover prevented effectively while the marking of the operator is made easier.

According to the invention the capacity of the system in which the incoming connecting traiiic passes over the numerical impulsing device used for the outgoing connecting direction can be appreciably increased in that the lines are not provided with particular accesses for the outgoing and incoming directions which are attainable over contact groups designated by different digits. The same access means to the .junction line is seized over the numerical impulsing device for outgoing and also incoming connections.

y be reached over the rst group selector and is used for incoming as well as outgoing connecting directions.

I. THE EMBODIMENT ACCORDING TO FIGS. 1 AND 2 l. OUTGOING CONNECTION When the subscriber Tnl makes a call the relay Ri is energised and in known manner gives rise to the setting of the preselector IVW. In the test circuit: -i, wiper l, contact segment 2, contacts 311, windings I and II of the relay Tl, wiper 4, conductor 5, contacts Bal, 1lcgw, the relay Tl is energised, disconnects the group selector IGW by short-circuiting its high resistance winding I at Contact 8H, stops the preselector and switches through the speaking conductors at contacts 925|, and I Utl, by disconnecting the calling bridge.

In the microphone feeding circuit the relay Al is energised but not the diierential relay XI. At contact Gal a short circuit of relay Cl is removed. The impulsing contact llal is opened and at contact lal the slow to release relay Vl is switched in. Relay VI is energised, closes its contact |312| in the circuit of the control relay V2 which however is short-circuited as long as contact I2a| is closed. At Contact Icl after the off-normal contact 1kgw is opened a holding circuit operating for the relays Cl and Tl, is completed. At contact I1cl the circuit for the vertical magnet and at contact lcl the test circuit are prepared.

The accesses for the connecting line in the outgoing direction are connected in the decade X of the group selector. The subscriber Tnl transmits a suitable number of impulse series. Relay Al transmits these impulses to the vertical magnet HI: -l, contacts Hal, I1cl, vertical magnet HI, rotary off-normal contact |8112, At the rst numerical impulses when contact I Zal opens and contact |9al closes relay V2 is energised: contact |312I, relay V2, winding I, contact IBaI, resistance 2D, It remains energised during the impulse series and prevents the premature operation of the rotary magnet Dl by opening the contact 2h22. At the end of the numerical impulse transmission and restoration of relay V2 the rotary magnet DI is switched in: interrupter, contacts 2213i, Zivil, rotary magnet DI, oil? normal contact 23kg112, When the wiper of the group selector reaches the contact of a further junction line VL, the test relay PI is energised: relay Vl, winding II, contact I8cl, windings I and II of the relay Pl, wiper 24, contact 25, locking conductor 28, contact 21h1', winding I of the relay C4 and parallel to this: contact 28121, differential winding II of relay C4, contacts 29121, 3071.1, M5128, The test relay PI stops the group selector by opening the contact 22pl. short-circuiting its high resistance winding I at contact 3 lpl, disconnects the relays Al and Xi at the contacts 32'pl, and 3312i and switches through the speaking conductors at contacts 34p| and 3511i. the Contact I412| in the holding circuit of relays CI and TI is closed. Relay AI restores and short-circuits the relay CI at contact Sal so that it restores. The relay Tl however remains energised over: Gal, 1412i, 3612i, I6.

At the junction line VL the seizing relay C4 switches through the speech conductors, at the contacts 31c4 and 3864. The calling subscriber is fed with current over the relay A4 which switches in the relay' V1, at contact 390,4. This opens the contacts 28121 and 29121. Moreover, a holding circuit is completed over both windings I and II and the contact 40c4 for the relay C4. and alsorfor the relay PI of the group selector. The

contact 4la4 in the upper conductor of the junction line VL is closed. At contact 42121 the choke Drl in the bridge between the two conductors ofthe connecting line is connected and thereby the call signal is transmitted to the distant exchange station.V Other contacts controlled by It locks the connecting line by The contact 36121 in series with the relays C4 and V1 are ineffective in outgoing connections.

2. INCOMING CONNECTION (a) Subscribers Zine free When a call is made over the junction line VL the relay Ar is energised and switches in a holding relay Hr at contact u1- the relay holding itself energised in a holding circuit at contact 45121: contacts IG0128, 48121, 41tr, 4611.1', relay H1', At contact 49111' the engaged lamp BLl and at the contact 501m', the calling lamp AL are switched in. The junction line VL is locked against seizing over a group selector by the opening of contact 3h1'. At contact 21h1' the locking conductor 26 is disconnected and at contact 5| hr the locking conductor' 52 is connected in the incoming direction and causes the operation of the locking relay C4 for the junction line VL. The calling of the required subscriber after this connection to the calling junction line VL causes relay Ra to be switched in: contact 53h', winding I of relay Ra', contacts 54ra, 55h13 56c4, Relay Ra holds itself energised at contact 51m opens the contacts 58m, 59m, in the speaking conductors, connects its winding II at contact m to the upper speaking conductor and at contact Slm connects the resistance 62 connected to positive to the lower speaking conductor.

The operator operates the supervisory switch AT. Relay Ab is energised and holds up over: contacts 63h", 64c4, 65u12, relay Ab, The contacts 56u19, 51ab, are opened and the contacts EBab and 69u12 are closed. The speaking apparatus BA of the operator is connected across the junction line VL. At contact 1Mb the choke Dr2 is connected across the two speaking conductors. At contact 1Ial2 the call lamp AL is disconnected. Further the circuit for the engaged lamp is opened at the contact 14al2. By closing the contact 'lab the setting up of the connecting path to the group selector is completed preparatory to calling over the junction line VL.

When the operator has obtained the necessary information, she presses that key of the set of keys at the exchange which corresponds to the number of the required subscriber. In metering transmission the contacts e are switched over into the operated position, and are controlled either by a relay or mechanically from the metering transmitter. At contact 15e relay Fl is switched in and by closing the contacts 19fl, llfl and opening the contacts 11fl, 18j! the conductors 83, 84 leading to the first selector PGW of the setting path are switched over to the metering transmitter and the relay F2 is switched in at contact 85H, so that the contacts SH2, 82f2 and 81/2 are closed. At contact 88e the relay G is switched in over its winding I. It closes the contact 89g in circuit of its winding II, contact 913g in the circuit of relay F2, contact Slg in the circuit of relay FI and the contact 92g in the circuit of relay GI. Over the contacts 89g and 92g no switching operations are carried out for the moment since the contacts 93e and 94e are open. The following circuit is set up over the contact 95e: impulsing contact 1', contacts 95e, 86gl, BOfI, 82j2, conductor 84. contact 91122, relay A2, The relay A2 switches in the relay V3 at Contact 98a2 and removes the short-circuit for the winding of rclay C2 at contact 99a2, the relay responding: resistance 8S, contact 81f2, conductor 100, relay C2, resistance lOl, The relay C2 prepares l 2,278,585 `v for the Isetting of the group selector PGW-of the setting path and prepares aY test circuit at the contact |2c2. `The setting magnets vof the selector PGWare not shown. Numerical impulses are -produced by opening the contact i and cause relay A2 to restore so that the impulses are transmitted further to the driving magnet. In known manner a control relay is also energised which,

during the impulse series, prevents the operation of the test relay P2 by opening the contact I03'u4. At the end of the impulse series contact |0304 is closed and the following locking circuit is completed: contacts I B202, I 03114, relay P2, wiper |04, winding I of relay C3, and parallel to this,

kcontacts |0505, Ia3, winding II of relay C3,`

off-normal contact IIi'llcpZw, The relay P2 opens the contact 91392 and switches through the setting path at the contacts IIlpZ and I09p2.

Contact I mp2 is opened and so prevents a shortcircuit of the locking relay C2 -at contact 99a2' when relay A2 restores. lIn the station line selector PLW relay A3 responds over its lower winding, the conductor 34 and the Contact i in the metering transmitter. It opens the contact I05a3 and switches in the relay V5 at contact II|a3 and also opens contact "15175. The relay C3 prepares the holding circuit at contact H203 over both its windings I and II after the olf-normal contact IIIIkpZw is opened and prepares the test circuit over the winding I of relay P3 and a circuit connecting up relay Y by closing the double armature operating contact H3c3.

During the rst numerical impulse 'series which sets the line selector a slow relay, not shown,

is energised which opens the contacts H4126 and II 512B. At the end of this impulse series the switching over of the line selector to the second setting magnet is carried out in known manner, when the relay, not shown, restores. The second impulse series, during which contacts H406 and H5226 are again opened, causes the setting of the line selector PLW on the connecting line of the required subscriber TnI. At the end of this impulse series the contacts H4116 and |5116 are closed. The connecting-uplrelay Y is'slow to energise. It is therefore not energised when the test relay P3 is energised owing to the selected connecting line being free: contacts, H303, H4116, winding I of relay P3, wiper H6, contact II rest contact H8 of the preselector IVW, wiper 4, windings II and I of relay TI, wiper I, On account of the high resistance of winding I of relay P3 relay TI is not energised in this circuit. In the line selector PLW the circuit of the connecting-up relay Y is broken at contact i I I9p3. At contact I2 |113 a holding circuit is prepared over the winding II of relay P3. At contacts I22p3 and |23p3 thedisconnection of both windings of bridge relay A3 follows and at the contacts I24p3 and I25p3 both conductoi's of the setting path areswitched through. Relay A3 restores and disconnects relay V5. At the con tacts I06a3 and I 5505 both windings I and II of relay C3 are short-circuited. The relay C3 restores. The relay P3,` whose winding I is disconnected at contactv I3'c3 remains energised: winding II of relay P3, contacts |2Ip3, I6a3, |0505, wiper |04 of PGW, relay P2, contacts |0304, I02c2,

In the metering transmitter the contacts e return to the rest positions when all the numerical impulses are transmitted. Before contacts-88e and 95e are opened the contact 93e' is closed. The relay G is held energised owing to the selected junctionfline being free and the line se- -3 lector PLW being switched through to the contacts |2412?,- and I2'5p3: contact I26`tI, conductor |21, wiper |28,Vcontacts |2911, I24p3, wiper I30,'contact IDBpZ, `conductor 83, contacts 8| f2, '|9fI, winding II of relay G, contacts 89g,v 93e, 96nd, SIlI, 82f2, conductor 84, contact |09p2, wiper I3I, contact I25p3, |3221, wiper |33, conductor |34, contact I35tI, relay vRI, The relay RI is energised and causes the seizing of a free group selector `IGrW in an outgoing direction. At the exchange theA koperator maintains contact 92g closed so that the relay GI with its slow armature attraction is energised: relay GI, contacts 929,*94e, resistance |35, Relay GI opens at'v contact I 3'IgI the shunt for its winding I switches through over its contact I38g| its winding II to the contact f| and thereby to the conductor 84 and holds relays FI and F2 energised over the contacts I39g| and I40gI.

In the group selector IGW, since after the reis energised over its winding II. At kcontact I2a| relay VI is connected and completes a holding circuit over the winding III of relay XI: contacts IllIuI, I42I, winding III of relay XI,

vRelay XI closes, at contact I43:1:I, a circuit over the vertical magnet HI and control nrelay V2 by which the group selector is raised to the decade IX in which the operations for the connection of an `incoming call to the connecting line ensue, interrupter, winding II of the relay V2, omormal contact I44kgw, which is openv when thehwiper is set on lthe decade IX, contacts |4314, IlcI, vertical magnet I-II, contact |810, The relay AV2 prevents premature operation of the rotary magnet DI at contact l2h12. Relay V2 restores when the decade IX is reached and contact I44kgw` is open and closes the circuit for the rotary magnet DI. The group selector 'hunts for an access to the calling junction line VL. When this is attained the test circuit is closed: -l, winding II of relayrVI, contact IBcI. windings I and II of relay P, wiper 24, contact |45, conductor 52, contact 5Ihr, winding I of relay-C4; and Contact 28111, winding II of relay C4, in parallel, contacts 29121, 15u11, I46'U8, The relay PI stops the group selector and disconnects the junction line at contact 3IpI. The bridge consisting of the relays AI and .XI isdisconnected by theV opening of the contacts 32m, 33pI','and at the' contacts 34p! and 35m the speaking conductors are switched through. Since inf'tlie Vaccess for the incoming connection the contacts I4'Ic5 and |4805 in the speaking conductors are still open, the relay GI in the operators exchange restores It disconnects the relays FI and F2 at the contacts |39y| and Iflgl. The selector which is set in the setting paths PGW and P LW is 4disconnected by the opening of contact 8`f2, for relay C2 `restores and opens at Contact I02c2 the circuit over 4the relays P2 and PEI which restore "andV step the selectors PGW and PLW into their rest position,

'Ihe relay C4 energises in thelocking circuit of the junction line V L closes'at contact I49c4'the circuit for the s'lowwto-respond switchingrelay C5; I, 001113210115 |4964.' 959mg relay C5, resistance I5I, At the contacts |4705 and |4805 the speaking conductors are switched through. `Since the relay Ra, as described above, is also energised the selected subscriber'IlnI is called. By a ringing current relay, not shown,l the contact |5211' is opened. At certain time intervals e. g. every 5 or 10 seconds at contact I53Zr the calling 6.11.1- rent is connected to the winding I I of relay Ra and also to the upper speaking conductor. When the called subscriber replies, a direct current owing over the differential winding II of relay Ra causes the relay Ra to restore, disconnects the calling apparatus at the contacts 60m and 6Ira and switches through the speaking conductors at contacts 58m and 55m.

The relay C4 prevents the disconnection of the choke DrZ from the holding bridge by closing the contact I54c4. It opens the circuit of the calling lamp AL at the contact 1204, switches in the engaged lamp BLZ at contact I55c4, breaks the holding circuit of relay Ab at contact 64c4 so that this restores, disconnects the branch to the speaking apparatus of the operator at the contacts 68ab and 69ab and switches through the speaking conductors at the contacts 66u12 and Slab.

After the speaking conductors are switched through at the contacts 58m and 59m, relay A4 responds in the microphone feeding circuit. It switches in the relay V1 at Contact 3911.4. Moreover it connects a holding bridge between the conductors of the junction line VL over the contacts 4|a4 and 4201 and the choke DTI. At contact I51v1 the choke Dr2 is disconnected. At contact |5801 a new holding circuit for the relay Hr is completed. The contact 482:1 is opened. At contact I 59121 the slow relay V8 is disconnected and by the opening of contact I46v8 in the energising circuit of the relay C4 makes possible the disconnection of the connecting path over the preselector I.VW and group selector IGW, at the end of the connection and by opening contact IBBUB ensures the restoration of relay Hr at the end of the connection.

When the subscriber 'Inl hangs up his receiver at the end of the connection the relays A4, V1 and V8 restore one after the other. By opening the contact 4|a4 the release signal is transmitted to fthe distant exchange station. At contact 28121 the windings I and II of relay C4 are shortcircuited. Contact 4904 is opened so that the relays PI and VI in the group selector restore and by the opening of the contacts I4v| and 36p| the restoration of the relay TI in the preselector LVW is also brought about. 'I'he group selector and the preselector are restored to their zero positions. The relay Hr is de-energised since the contact |5801 is opened. The relay C4 is prevented from remaining energised over the contact 29121 and the relay Hr over the contact 481:1 by the slow relay V8 which holds the contacts I46v8 and I 60128 open until the relays C4 and PI or Hr have restored.

(b) The subscribers Zine engaged A3, however, remains energised. At the contact 92g the relay GI is disconnected before it can attract its armatures. At contact 9|g the relay FI is disconnected and closes its contacts 11fl and 1811. Relay Br is bridged across the conductors 83 and 84 and is energised and at the contact |62br a new circuit for the slow relay F2 is closed that holds the contacts 8If2, 82f2, and 81f2 operated further, At contact I63br the engaged Vlamp BL2 is switched in, and serves as a signal for the operator when alight that the junction line of the selected subscriber is engaged. If now the switch HT is operated and thereby switched from the branch of the junction line VL to the conductors 83 and 84 of the setting path the operator is connected with the selected subscribers line (Tnl), for in the nal selector LW the connecting-up relay Y is operated since relay P3 is not energised and by opening contacts |2911, I32y and closing contacts |63y, I64y the wiper switches through the speaking conductors.

If the calling subscriber is ready to receive the connection in question he puts down his handset and causes thereby the disconnection of the existing connection. The operator then operates the key DT. At contact I65dt the relay Br is disconnected. The engaged lamp BL2 is lighted. Relay F2 is prevented from restoring by the closing of contact I61dt. At contact I66dt relay O is connected to the conductors 84. The relay O is an insensitive relay which in series with winding II of the relay A3 in the exchange nal selector PLW is not energised.

If after the preselector LVW has returned to its zero position the test relay P3 of the exchange final selector PLW is energised, relay Y is disconnected (at H9133) and at the contacts I24p3, |291/ and |25p3, |3211, the conductors of the setting path are switched through, the relay O is energised in series with the relay RI connected to the junction line. It holds itself energised over the contact |680, which is parallel to contact IGSdt and again connects the engaged lamp BL2 as a signal to the operator that she can return to normal the key DT. Relay F2 is held energised over the contact Io. After seizing the group selector I GW the group selector is set in the manner described in Section Ila. If contact 339| is opened, the relay O is deenergised at the operators station and disconnects the engaged lamp BL2 and the relay F2. The setting path PGW, PLW is disconnected.

II. EMBODIMENT ACCORDING TO FIG. 3

The junction lines VL are equipped with a single access only which is employed for outgoing as well as incoming connections.

Connections to outside exchanges are set up in the manner described for the calling subscriber in Section I, 1.

An incoming call from the exchange in the opposite direction and the setting of the path consisting of the selectors PGW and PLW follows as explained in Section I, 2.

(a) Subscribers line free The relay XI in the group selector IGW, which after the preselector LVW is set is energised in the circuit over the conductors 84 and |34, closes,

at contact I42.r|, a holding circuit over its winding III and over the winding III of the relay AI. The circuit of the vertical magnet HI is closed at the contact I43l. This circuit is opened at contact I44lcgw when the group selector has reached the decade X in which the line is connected.

Relay XI by opening the contacts IBUI, IBIzvI has disconnected the bridge across the speaking conductors and by closing the conductors I82:r|, |8311, I84xl, I85| has prepared a test circuit over the speaking conductors connected in parallel and the relay Pal. The contact 2|0| in the test circuit over the wiper 24 is opened. Thus,

the test relay PI is prevented from energising during the hunting for the calling vjunction line VL.

At the operators exchange, the relay Gl has set up, on being energised, a circuit over the relays N and M; contacts HSSUS, |8104, relay M, contact |88hr, relay N, contact |39gi, Relay N completes a holding circuit at contact |9371.. It holds the relay F2 energised, further over the Contact |9271, opens the contacts |9311., |9411, and connects the conductor leading to the setting path over the contacts |9511., ln with the test apparatus consisting of the test relay PaZ and the repeater Ue. The relay M of the junction line VL prepares the locking circuit at contact,

After contact lilla?! in the group selector is opened relay GI restores. Relay Fl is disconnected. Contacts Tijl and 78j! are closed.

At the end of the vertical adjustment of thel group selector LGW, the circuit over the rotary magnet DI is closed at contact 2h22. When the Wipers of the group selector reach the contacts of the calling line VL a test circuit is set up over all the connecting apparatus in use and is fed from a source (repeater Ue) at the cperators exchange, which circuit extends over the speaking conductors of the setting and speaking path connected in parallel: secondary winding s of the repeater Ue, condensers kol/R02, contacts |95n/l96n, 'Fifi/IEN, SH2/3212 conductors 83/84, Wipers ISB/ISI, contacts |29y/I32y, wipers |2/l33, conductors IBI/|353, contacts BIH/mtl, wipers 2D2/2il3, contacts 32pI/33pl, |82aIl/l83axl, relay Pal, condensers 1co3/Ico4, contacts lllrl/izri, wipers 284/205, contacts 206m/2mm, condensers lcoii/lco, relay Pa2, secondary winding s of the repeater Ue. An alternating current source, for instance the calling source, is connected to the primary winding par of the repeater Ue.

The relay Pal stops the group selector by opening its contact 2ilpa| and closes at contact 201pa| the test and switching circuits over the wiper 24 of the group selector.

Relay Pa2 disconnects the locking circuit at Contact 208pa2. Moreover the relays Pi and C4 are energised: -Winding II of relay Vl, contacts'201pal, |8cl, windings I and II of relay Pl, Wiper 24, contact 25, winding I of relay C13, contacts 29N, mlm, 2D8pa2, The'relay PI opens the contact 22M `in the circuit of the rotary magnet DI, short-circuits its own winding I at contact 3|pl `and the contacts |8cl, Elpa, disconnects the test circuit by opening the contacts 32p| and 33p| and switchesthrough the speaking conductors at the contacts SMDI and 3512i. At Contact 209m the holding circuit is broken over the winding III of the relays A-Il and Xl. The relay C4 holds itself energised at contact 2| ict in a circuit independent of the contacts mlm and 20810112 and prepares a further holding circuit at contact 4004 operative after contact 28e? and 29211 are open. At contact I8'lc4 the circuit is opened over the relays M and N. At the contacts I 98m and |99m thespeaking conductors are is called. At contact 5821i relay F2 is disconnected, the selectors PGW and PLW are disconnected.

switched through. The selected subscriber Tnl (b) Subscibcrs Zine engaged l the test relay of the exchange iinal selector PLW cannot energise because the line is engaged, the switch operations described Vin Section I, 2b take place at the operators exchange. The relays G and Fl restore. Relay Br energises, holds the relay F2 and switches in a signal for the operator. The operator connects herself to the required subscriber Tnl, to which line she is connected by the closing of the contacts |631/ and |5411. She operates the key DT and switches in the winding I of relay O, which when the line is free and contacts |25p3 and |321/ are closed is energised in series with the relay Rl. The relays M and N are connected at contact 2150 and relay O holds itself energised at contact |690. Since this holding circuit is disconnected after the marking signal for the incoming connection is received by the group selector iGW a holding circuit is set up over the winding II of the relay O at contact M30-independent of Contact 2|411.. After the group selector LGW is set on the calling line and the locking relay Cd is energised,

the relays M and N are disconnected. At con-V tact 2mn the holding circuit over the winding circuit of relay O is opened so that it restores. rIhe disconnection ofthe setting path follows and thev speaking connection is terminated.

III

The test circuit with a source of current as used in the embodiment according to Fig. 3 can naturally also be utilised in systems in which incoming connections are set up over separate accesses to the junction line. In systems in which outgoing and incoming connections are over the same accesses to the junction line, the use of a test circuit with a singular source is not absolutely necessary, if even convenient, since in this adaptation the simultaneous setting up of several incoming connections is possible without locking the outgoing direction.

The test circuit with its singular source extends in the given embodiment over the speaking conductors of the setting path connected in parallel consisting of the selectors PGW and PLW and the selectors LVW and LGW of the speaking path: subscribers line calling connecting line. It can also extend over only one of the speaking conductors an auxiliary conductor, or for example, over the test and locking conductors of the particular selecting stage coupled by condensers.

I claim:

1. In a telephone exchange having trunk lines to another exchange, subscribers lines, switching apparatus operable on an outgoing call from one of said subscribers lines to extend a connection from the calling line to one of said trunk lines, and means operated on an incoming call received over one of said trunk lines to select the desired subscribers line and then to-operate said apparatus to extend a connection from the selected subscribers line to the trunk line over which said incoming call was received.

2. In a telephone exchange having trunk lines to another exchange, subscribers lines, switching apparatus adapted to be operated directively on an outgoing call from one of said subscribers lines to extend a connection from the calling line to one of said trunk lines, means operated on an incoming call received over one of said trunk lines to select the desired subscribers line, and means controlled by said selecting of the desired subscribers line by said last means for operating said apparatus exclusively as a hunting means to find the trunk line over which the incoming call was received and extend thereto a connection from said desired line.

3. In a telephone exchange having trunk lines to another exchange, subscribers lines, switching apparatus having access to said trunk lines and to other lines, means for operating said apparatus directively to said trunk lines on an outgoing call to said other exchange, means including a test circuit for then causing said apparatus to search automatically for an idle one of said trunk lines and extend a connection thereto from the calling subscribers line, means operated on an incoming call received over one of said trunk lines to select the `desired subscribers line, and

means including another test circuit for then operating said apparatus exclusively as a hunting means to find the trunk line over which the incoming call was received and extend thereto a connection from said desired line.

4. A telephone exchange as claimed in claim 3, wherein one of said test circuits extends over a line conductor of the connection, and wherein the other of said test circuits is independent of the line conductors of the connection.

5. A telephone exchange as claimed in claim 3, wherein said selecting means includes means for extending a temporary connection to the desired subscribers line, and wherein said other test circuit extends over said temporary connection.

6. In a telephone exchange having trunk lines to another exchange, subscribers lines, switching apparatus adapted to be operated on an outgoing call from one of said subscribers lines to extend a connection from the calling line to one of said trunk lines, other switching apparatus, means for operating said other switching apparatus on an incoming call over one of said trunk lines to extend a connection to the desired subscribers line, means for then operating said rst switching apparatus to extend a connection from said desired line to the trunk line over which said incoming call was extended to the exchange, said last means including a testing circuit extending over the connection extended by said other switching apparatus to the desired line, said circuit effective to prevent said first switching apparatus from extending a connection to any of said trunk lines except the one over which said incoming call was received.

7. In a telephone exchange having trunk lines to another exchange, subscribers lines, switching apparatus operable on an outgoing call from any of said subscribers lines to extend a connection from the calling line to one of said trunk lines, normally idle marking means, means effective on an incoming call over one of said trunk lines to seize said marking means, means for then operating said marking means to characterize any desired one of said subscribers lines as a called line, means controlled by said characterizing of the desired line for thereupon automatically operating said switching apparatus to extend a connection from the characterized line to the trunk line over which the incoming call was received, means for releasing said connection at the end of the call, and means for releasing said marking means before and independently of said release of the connection.

8. In a `telephone exchange having trunk lines to another exchange, subscribers lines, a switch common to said lines, means for seizing said switch on an outgoing call from any one of said lines and operating it to extend a connection to one of said trunk lines, means operated on an incoming call over one of said trunk lines to select the desired subscribers line, and means controlled by said last means for seizing said switch and operating it to extend a connection to the trunk line over which said incoming call was received.

9. In an exchange as claimed in claim 8, a iirst test circuit in said switch eiective only on outgoing calls to prevent said switch from connecting with busy trunk lines, and a second test circuit effective only on incoming calls to prevent said switch from connecting with any trunk line except the one over which said incoming call was received.

10. In a telephone system, an exchange, subscribers lines terminating at the exchange, a two-way trunk line outgoing from the exchange, switching apparatus in the exchange having access to said trunk line over a plurality of paths, means for operating said apparatus on outgoing calls to connect the calling subscribers line to said trunk line over one of said paths, and means for operating said apparatus on incoming calls to connect the called subscribers line to said trunk line over a different one of said paths.

l1. In a telephone system, an exchange, subscribers lines terminating at the exchange, a two-way trunk line outgoing from the exchange, switching apparatus in the exchange common to said subscribers lines and having access to Said trunk line over a plurality of paths, means for operating said apparatus on an outgoing call from any of said subscribers lines to connect said calling subscribers line to said trunk line over one of said paths, and means for operating said apparatus on an incoming call to any of said subscribers lines to connect said called subscribers line to said trunk line over a diierent one of said paths.

12. In a telephone system, an exchange, subscribers lines terminating at the exchange, a, plurality of two-way trunk lines outgoing from said exchange, a switch in said exchange having access to each of said trunk lines over one path for outgoing calls and over another path for incoming calls, means for operating said switch on an outgoing call from any of said subscribers lines to connect the calling line to an idle one of said trunk lines via its outgoing call path, means operated on an incoming call over any of said trunk lines to select the desired subscribers line, and means controlled by said selecting of the desired line for then operating said switch to connect said desired line, via the incoming call path of that trunk line, to the trunk line over which said call was extended to said exchange.

13. In a telephone system, subscribers lines, automatic switching apparatus common to said lines, means responsive to a calling condition on one of said lines for seizing said apparatus, means for controlling said apparatus over the calling line to extend a connection t0 a called line, an operators position for controlling the extension of calls to said subscribers lines, means controlled from said operators position when a call is to be extended to one of said lines for simulating a calling condition on that line, thereby to cause said rst means to seize said apparatus, and means controlled from said operators position for then operating said apparatus to extend a connection to the line by which said last line is called.

14. In a telephone system, two groups of lines, switching apparatus common to said lines, means responsive to a calling condition on any line of one group for seizing said apparatus, means for then controlling said apparatus over said calling line to extend a connection to a line of the other group, means operated when a call is to be ex- 10 

